In general, almost all the electronic components mounting machines have so far been provided with capabilities of applying a correction to mounting operations according to deformations observed on a substrate where electronic components are mounted.
Such a correction applied to prior art electronic components mounting machines will be explained with reference to FIG. 8.
In FIG. 8(a), recognition marks 2 and 3 are located on each of two corners of a substrate 1, respectively, where the two corners are situated diagonally opposite to each other. With a prior art electronic components mounting machine, when the substrate 1 is deformed from an ideal configuration as indicated by solid lines in FIG. 8(a) to a configuration indicated by dotted lines, the position of the recognition mark 3 is shifted accordingly. A constant deformation ratio is obtained by calculation from the magnitude of shifting of the recognition marks 2 and 3 and a correction is applied to mounting positions of the electronic components mounting machine by the use of the deformation ratio. In this case, however, it is assumed that the deformation of the substrate 1 is taking place uniformly in both the X and Y directions as illustrated in FIG. 8(a).
When deformations appear nonuniformly in the X and Y directions as shown in FIG. 8(b), the two recognition marks 2 and 3 do not provide correct information on the deformations, thereby not allowing the derived deformation ratio to represent the actual deformations of the substrate 1. Particularly, as large size substrates are used more and more recently, the adverse effect of nonuniform deformations is no longer neglected.
Thus, the prior art electronic components mounting machines have presented a problem of inability to cope sufficiently with the deformations of substrates when large size substrates are used and/or a high precision mounting performance is required of electronic components mounting machines.